3. The criteria are—
(a)in the case of improvement measures specified in paragraph 2(c) to (f), the reduction, as estimated in accordance with an approved methodology, in the cost of the energy consumed in the building or building unit over a period of 7 years after the date on which the measure is carried out would be greater than the cost of carrying out the measure; and
(b)in the case of the improvement measure specified in paragraph 2(g), the boiler to be replaced is more than 15 years old.